1. Field of the Invention
The invention pertains to a locking system for motor vehicles, consisting of a lock to be actuated by a grip on at least one door, tail gate etc. of a vehicle. The lock can be switched between two different positions, namely, a secured position which makes the grip inoperative and another position which allows the grip to operate, in which position the lock is to be opened by actuation of the grip. A sensor, located near the grip and connected to an electrical control unit, initiates the process by which a data storage medium, held by the operator, is interrogated for data by the electrical control unit. The electrical control unit is connected to a send/receiver unit and transmits via this unit the data request to the data storage medium held by the operator. The data storage medium transmits its data from the data unit via a transmitter to the send/receiver unit into the vehicle. The send/receiver unit passes the data along to the electrical control unit. The electrical control unit, in the event of a positive data identification, orders the release of the lock or locks on at least one door, tail gate, etc. of the vehicle. In a locking system of this type, access authorization is checked by a process of electromagnetic data interrogation. The area of application of the invention is intended especially to include motor vehicles, accesses to security zones, etc.
2. Description of the Related Art
In a locking system of the type indicated above, it is known that a person can be given access to, for example, a motor vehicle, by way of the data interrogation of a data storage medium such as a check card. The process of data interrogation is initiated in this case by a mechanical switch or sensor, e.g., a light barrier, attached to the vehicle, this switch being installed on a door handle or at least in the area of a door handle. By actuating the switch, or, expressed more accurately, by a moving the handle or by passage of a hand through the light barrier, the person desiring access initiates the process by which a control unit in the vehicle, for example, requests data from the data storage medium. The pulse thus triggered is sent by the control unit to a transmitter, which transmits the request for data to the data storage medium. The data storage medium receives the data interrogation command and sends it to a data unit, which passes on the requested data to a transmitter. The transmitter then sends the data back to the send/receive unit on the vehicle, and from there it goes to the control unit in the vehicle. If the control unit establishes positive data recognition, it issues a command to release the locking system.
The data interrogation process therefore does not begin until after the handle, such as the stirrup-shaped or flap-shaped grip of a door handle, has been actuated. Because there are still several steps which must follow the actuation of the handle, the interrogation process begins at a relatively late point in time, as can be derived from the above description. This delay in the data interrogation and the time it then takes for the a central locking system to respond make a system of this kind inconvenient. In many cases, the result is that the locking system is not released the first time the handle is actuated, and the person desiring access must actuate the handle a second time to open the door.
A locking system for locking a motor vehicle in which the data interrogation of a transponder is initiated inductively by an induction coil mounted on the vehicle near the handle is known from DE 44 35 894 A1. The person desiring access initiates the data interrogation of the transponder by approaching the vehicle equipped with the induction coil, and the transponder is thus addressed. The transponder then transmits the data stored in it, i.e., an identification code, to a control unit, which checks the access authorization. If the control unit makes a positive recognition of the data, it gives the command to release the locking system.
In the device described above, it is disadvantageous that the locking system can be released unintentionally if, after the locking process, the user unintentionally or accidentally approaches the vehicle again after it has been locked by the safety device described.
A design for unlocking and monitoring a locking system is known from DE AS 15 66 733. In this design, the data storage medium consists of an LED, which is attached to a portable transmitter. A receiver, which is located on the locking device on the door, is connected to an electronic control unit, which evaluates the incoming signal from the portable transmitter. To release the locking system, the user must aim the portable transmitter with the LED at the receiver on the locking device and thus actuate the transmitter. The light signal emitted by the transmitter, which has a characteristic wavelength, is then received by the receiver and transmitted to the control unit, which checks to see whether or not the light frequency emitted by the transmitter is the same as the preset value. If the frequencies match, the control unit releases the locking device.
The disadvantage here is that the user is required to perform awkward actions, in that he must aim the transmitter accurately at the receiver on the locking device. This makes the system inconvenient to operate.
A locking system which consists of an infrared transmitter and several infrared receivers, which are mounted on the vehicle near the outside skin of the vehicle and which control the locking system, is known from DE 36 21 592 C1.
To release the locking system, the user is required in this case, as already explained in the previous case, to aim the portable transmitter with the IR diode at the receiver on the locking system and thus to actuate the transmitter. The IR beam emitted by the transmitter is then analyzed by the receiver, which checks to see whether or not the light frequency emitted by the transmitter is the same as the preset value. If the frequencies match, the control unit releases the locking device.
The disadvantage is present here, too, that the user himself must perform awkward actions, in that he must aim the transmitter accurately at the receiver on the locking system, which makes the system inconvenient to use.
A built-in push-button unit for vehicle doors is also known from DE 34 40 442 A1l. This switch has two push-button elements, which can be used to actuate a microswitch.